Mössbauer measurements in CuFeTe 2 (original) (raw)
SDW in the 2D Compound CuFeTe 2
Hyperfine Interactions, 2001
In a previous work (ICAME'97) we presented the Mssbauer results for a non-stoichiometric sample of the quasi-two-dimensional (2D) dichalcogenide CuFeTe2, where a Spin Density Wave (SDW) ground state with T SDW=25615 K was proposed. Here we report the study of the magnetic and electric properties determined by magnetic susceptibility, Mssbauer spectroscopy and resistance measurements, of an almost stoichiometric sample prepared by the vertical Bridgman growth technique. The SDW behavior is supported by the results obtained by the following different techniques: Magnetic susceptibility: A magnetic transition is observed at T SDW=308 K with a Pauli paramagnetic behavior above this temperature. Mssbauer effect: The shape of the spectra and the thermal evolution of the hyperfine field are characteristic of the SDW's in quasi-2D systems. Electrical resistance: There is a metal–semiconductor transition along the layers as the temperature decreases indicating the opening of a gap ...
2010
In the tetragonal crystalline structure of MnxFe1−xSe0.85, the magnetic state contains low-and high-spin Fe 2+ , with high-spin numbers equal to that of the combined Mn substitute and Se deficiency atoms. The state is pinned by "spin-hopping" around substitution centers via highspin ↔ low-spin conversions. During the structural distortion from tetragonal to orthorhombic, from 90 K to 70 K, the rate of spin conversions increases and the iterant character of the magnetic state is enhanced. In the orthorhombic structure, the spin dynamics evolve into an incommensurate spin-density wave (ISDW). Excitations of the ISDW decrease with temperature and level out across the superconducting phase. The ISDW appears to have more than one oscillation mode and contributions from high-order harmonics.
Journal of Magnetism and Magnetic Materials, 2013
Iron-vanadium sulfides of the monoclinic system Fe x V 3 À x S 4 (1.0 r x r 2.0) have been investigated by 57 Fe M össbauer Spectroscopy in the temperature range 30-300 K. Incommensurate spin density waves (SDW) have been found in this system. An alternative treatment of the spectra allows a direct measurement of the temperature evolution of condensate density of the SDW state which follows the Maki-Virosztek formula. For composition (x ¼ 1.0) the SDW condensate is unpinned while for compositions (x 4 1.0) the SDW condensate is pinned. Possible causes of the pinning-unpinning SDW will be discussed.
Spin Waves in the (π,0) Magnetically Ordered Iron Chalcogenide Fe_{1.05}Te
Physical Review Letters, 2011
We use neutron scattering to show that spin waves in the iron chalcogenide Fe 1:05 Te display novel dispersion clearly different from both the first principles density functional calculations and recent observations in the related iron pnictide CaFe 2 As 2 . By fitting to a Heisenberg Hamiltonian, we find that although the nearest-neighbor exchange couplings in the two systems are quite different, their nextnearest-neighbor (NNN) couplings are similar. This suggests that superconductivity in the pnictides and chalcogenides share a common magnetic origin that is intimately associated with the NNN magnetic coupling between the irons.
Evidence of magnetic broadening in Mössbauer spectra of superconducting FeTe 0.8 S 0.2
Hyperfine Interactions, 2013
Magnetic properties of the FeTe 0.8 S 0.2 superconductor were studied by Mössbauer spectroscopy. Low-velocity Mössbauer spectra that were recorded in the temperature range from 5.7 K up to 300 K show a paramagnetic doublet with a broadening at temperatures below 77 K. The broadening can be explained by the appearance of a distribution of hyperfine magnetic fields due to the magnetic ordering of a part of the sample. The magnetically ordered fraction starts to decrease at temperatures below 20 K indicating a possible competition with the onsetting superconductive state.
Physical Review B, 2011
Polarized Raman-scattering spectra of non-superconducting, single-crystalline FeTe are investigated as function of temperature. We have found a relation between the magnitude of ordered magnetic moments and the linewidth of 1g A phonons at low temperatures. This relation is attributed to the intermediate spin state (S=1) and the orbital degeneracy of the Fe ions. Spin-phonon coupling constants have been estimated based on microscopic modeling using density-functional theory and analysis of the local spin density. Our observations show the importance of orbital degrees of freedom for the Fe-based superconductors with large ordered magnetic moments, while small magnetic moment of Fe ions in some iron pnictides reflects the low spin state of Fe ions in those systems.
63,65Cu NMR study of the magnetically ordered state of the multiferroic CuFeO2
Journal of Magnetism and Magnetic Materials, 2020
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Physical Review B, 2013
Ground state and low-energy excitations of the quasi-one-dimensional antiferromagnet CuSe2O5 were experimentally studied using bulk magnetization, neutron diffraction, muon spin relaxation and antiferromagnetic resonance measurements. Finite interchain interactions promote longrange antiferromagnetic order below TN = 17 K. The derived spin canted structure is characterized by the magnetic propagation vector k = (1, 0, 0) and the reduced magnetic moment m = [0.13(7), 0.50(1), 0.00(8)]µB . The values of the magnetic anisotropies determined from the field and angular dependencies of the antiferromagnetic resonance comply well with a previous electron paramagnetic resonance study and correctly account for the observed magnetic ground state and spin-flop transition.